Aircraft with retractable landing gear are typically provided with retractable landing gear doors that operate synchronously with the landing gear for movement between open and closed conditions in response to landing gear extension and retraction cycles, respectively. Conventional landing gear doors must therefore be equipped with an actuation system or mechanism that open and close the doors during normal landing gear extension and retraction cycles, respectively (i.e., so that the gear doors are moved into an open condition out of potential physical contact with the landing gear during a gear extension cycle and moved into a closed condition covering the landing gear once the gear has been retracted during a retraction cycle).
There are two general classes of aircraft landing gear door actuation systems, namely (1) door actuation systems which are linked to the landing gear, and (2) door actuation systems having their own dedicated actuation system separate from the actuation system of the landing gear. Door actuation systems having their own dedicated actuation system must also be equipped with a dedicated extension system to allow the doors to open/close in the event of a failure of the landing gear actuation system. Thus, such door actuation systems must also be provided with a back-up system to allow the gear doors to open in order to allow the landing gear to extend in a gravity free-fall condition (e.g., a situation in which the landing gear extension is activated only by means of gravity without the aid of the normal on-board electric and/or hydraulic gear extension mechanisms.
Various emergency landing gear door operating mechanisms are known in the art, e.g., as evidenced by U.S. Pat. No. 9,102,403, U.S. Pat. No. 7,178,759 and US Patent Application Publication No. 2005/0194496 (the entire content of each being expressly incorporated hereinto by reference). There are, however, certain situations where the emergency landing door system needs to physically lift the landing gear door during a door opening operational cycle. For example, landing gear doors of cargo aircraft that have the door articulation axis close to the ground need to operate with a relative lifting movement in order to open the door and place it in a higher position thereby protecting the door from debris or contact with the ground should a hard landing event occur or a landing when the aircraft is in a roll attitude.
As noted above, landing gear door mechanisms having an independent actuation system require a back-up system in order to allow the landing gear door to open in the event of normal actuation system failure. In such a case, the back-up system for landing gear doors that require a relative lifting motion during the opening cycle needs to generate enough force to open and lift the door into its opened condition. Once opened, the system needs to also provide enough force maintain the door in an opened condition during various standard and non-standard landing events, e.g., a hard landing event. The force required to open and maintain the door in an opened condition can be generated by many means as compressed gas (e.g., air or nitrogen), air springs, pyrotechnic devices, aerodynamic or mechanical springs. In those cases whereby the landing gear doors need to be lifted into an opened condition, the system thus needs to generate even greater force so as to support the weight of the door weight and maintain it a locked and opened condition.
It is therefore towards providing solutions to the problems associated with emergency landing gear door actuation as noted above that the embodiments of the present invention are directed.